1. Field of the Invention
The present invention relates generally to a read head portion of a magnetic head for a hard disk drive, and more particularly to a giant magnetoresistance (GMR) read head including a free magnetic layer with closely spaced, horizontally aligned hard bias elements in two side regions.
2. Description of the Prior Art
In a commonly used giant magnetoresistance (GMR) read head, a GMR read sensor is located in a central read region, while a hard bias layer and electrical contacts are located in each of two side regions. The GMR read sensor typically includes nonmagnetic seed layers, an antiferromagnetic pinning layer, ferromagnetic pinned layers, a nonmagnetic spacer layer, a ferromagnetic free layer, and a nonmagnetic cap layer. The hard bias layer typically includes a seed layer and a magnetic hard bias layer. The electrical contacts typically comprise highly electrically conducting nonmagnetic layers.
The hard bias layer must exhibit a high coercivity and thus provide a magnetic biasing field for stabilizing the free magnetic layer. This stabilization is the most effective when the midplane of the hard bias layer is located at the same horizontal level as the midplane of the free magnetic layer. In the prior art head fabrication process, however, the hard bias layer is typically deposited on an Al2O3 bottom gap layer in the side regions, and thus the midplane of the hard bias layer is typically located at a horizontal level significantly lower than the midplane of the free magnetic layer. As a result, it is difficult to stabilize the free magnetic layer. In an effort to raise the hard bias layer, a thickened seed layer has been deposited beneath it. However, the deposition of such a thickened seed layer results in thick sidewall deposition upon the central sensor layers, thus creating an unwanted separation between the side edges of the free magnetic layer and the hard bias elements. Minimizing this separation is important to improve magnetic head performance.
There is therefore a need for a head fabrication process in which the hard bias elements are fabricated as close as possible to the free magnetic layer, and wherein the midplane of the hard bias layer can be located at the same horizontal level as the midplane of the free magnetic layer, so that the most effective stabilization of the free magnetic layer can be obtained.